RealClimate logo

Live (almost) from AGU–Dispatch #2

Filed under: — raypierre @ 12 December 2007

Before I get started with a few hasty remarks on today’s events, let me remind you that Lonnie Thompson’s Frontiers in Geophysics lecture will be webcast live on Wednesday at 1815 Pacific time. A link to the webcast can be found here. The lecture is entitled “Abrupt Climate Change and Our Future”. At the same page you’ll find links to Arvidson’s Whipple lecture on Mars exploration, which will be webcast at 14:20. Enjoy! Wish you were here.

Now, let me say at once how inspiring it is to see so much first-rate innovative science arrayed here. There are a lot of geophysicists in the world, and most of them are very, very good. It is especially encouraging to see so much new, young talent in all areas. I spend all too much of my time on RealClimate writing about bad science, it is great to come here and get a reality check.

I spent a fair chunk of my morning at the session at which I myself was giving a talk. This session was “Studying Climate Dynamics with Idealized Atmospheric GCM’s,” and was one of the few sessions devoted to basic fluid dynamical issues having a bearing on how climate works. By “idealized GCM’s” one means things like simplifying the radiation or continental configurations or thermodynamics, but retaining all or most of the fluid dynamics. What this really is about is how to design GCM simulations so as to test hypotheses and develop general understanding. That sort of thing doesn’t usually come from the fanciest and most comprehensive model. This session included such things as the way storm scale (“baroclinic”) eddy feedback helps determine the North Atlantic Oscillation. or how the sharpness of tropical sea surface temperature gradients determine the nature of the Intertropical Convergence Zone (an especially fascinating talk by Tim Dunkerton and colleagues). I myself was presenting a potpourri of some of the dynamical issues in my work on Titan and on the Snowball Earth postglacial hothouse — e.g. the reason that precipitation fails to rise as fast as Clausius-Clapeyron would suggest (which has some commonalities with methane precipitation limitation on Titan, where you only have 2 Watts per square meter to drive all the hydrological cycle). We had a quite good audience, but not the kind of SRO crowd that the Greenland Glacier session had. It can’t escape one’s attention that the amount of interest in and attention paid to basic fluid dynamical issues in climate is a lot less than what is going into some other areas. Someday, the balance will need to be restored. One problem is that fluid dynamics is really hard, and it is even harder to get into the newspaper with it, because it’s hard to explain to people. That makes it have less flash, though it’s none the less important to the understanding of climate. Still, a good time was had by all.

For me, the high point of the day (apart from an impromptu and wide-ranging conversation with Kevin Zahnle on SO2 photolysis, problems that have emerged with some classic Methane Early Earth radiative calculations, the possibilities of N2O as a greenhouse gas on the young Earth, and the general issue of oxygenation of planets) was Mark Serreze’s Nye Lecture on Arctic climate change. The tough part of that was that (as seems to be a law of the Universe) the Gods of Scheduling at AGU scheduled Mark’s talk right on top of David Lea’s Emiliani lecture on tropical climate change during the Last Glacial Maximum. So, one had to decide whether to go Cold or go Warm. I had been struggling with this decision all day, but in the end the decision was made for me since Mark’s talk was closer to the beer and by the time I was done talking to Kevin, there was no time to get over to Moscone West for David’s talk.

Needless to say, Mark spoke to a huge ballroom, and it was packed to the gills. This really is the Year of the Ice. He opened by showing some quotes from his earlier papers. Seven years ago, big changes in the arctic were clearly observable, but he wouldn’t have said with confidence that they were due to anthropogenic global warming (AGW). The problem is that the Arctic is subject to a lot of natural variability, notably the North Atlantic Oscillation (NAO). There was NAO-related warming in the period 1920-1940, so how could we know that the current warming wasn’t part of the same thing?

What changed Mark’s mind was that improvements in climate models made it easier to see the anthropogenic component of climate, as did a few more years of the AGW signal rising above the background variability. This is true not just for global means, but for regional climate. More importantly, there as been a persistent warming and sea ice retreat despite circulation changes (e.g. NAO going neutral) which should be forcing ice the other way. Mark said that the circulations that used to help you don’t help you build sea ice anymore, and the ones that hurt are now hurting more. That latter effect is intimately connected with a general thinning of sea ice,which makes it more vulnerable.

Models are getting good, he pointed out, but reality is exceeding expectations. Since 2005 there has been a 25% decline in Arctic sea ice at the time of minimum, equal to the combined area of Texas and California. What’s more, the drop in 2007 was way below the already steep trend line for 1978-2002. Factors contributing to the unusual 2007 drop include an unusual pattern of atmospheric circulation, with high pressure over the Central Arctic and low pressure over Siberia. This brings a lot of warm air into the Arctic. How does this fit into the longer term pattern? It comes back to the thinning again: the sea ice was so vulnerable to this situation (which has happened before) because it is so thin.

He compared sea ice trends between observations and the IPCC Fourth Assessment Report models. The observed rate of ice loss is much faster than expected. Even before 2007, the downward trend is at least twice the GCM trend, and 2007 is of course way more extreme than even that. The GCM’s say that 40% of the sea ice loss is anthropogenically forced between 1953 and 2007, and if you just count from 1979, it’s more like 50%. But that’s the GCM’s. In reality, given the extreme observed loss, the anthropogenic component may be much greater. It’s the ice thickness again: GCM’s seem to be overestimating ice thickness.

Other big changes are happening. Igor Polyakov’s results show pulses of increasingly warm Atlantic water, seen in moorings at Svinoy and Fram Strait. Also, there are feedbacks associates with Pacific summer water: Loss of sea ice means the atmosphere warms more, and that helps shunt more Pacific summer water farther into the Arctic Ocean, melting yet more sea ice, etc.

Are we at a tipping point, Mark wonders? He pointed to an NCAR simulation with the model CCSM3, which shows a gradual sea ice decline until 2020, but then a kick from an atmospheric fluctuation causes a sudden near-total disappearance of the thinned ice, which was primed to pop. The state of ice thickness observed in 2007 is quite similar to the modelled state in 2020. Mark suggests (my paraphrase) that 2007 is the new 2020.

Is the 2007 drop the first harbinger of a shattering drop like the NCAR model has in 2020? We’re close to the critical ice thickness now, based on IceSat data. Will 2007 be remembered as the tipping point for sea ice? Only time will tell.

Based on a detailed comparison of observed patterns of Arctic warming with GCM patterns including anthropogenic forcing, Mark declared confidently that “Arctic Amplification is Here.” The simulated patterns are spot-on the observed patterns, both with regard to seasonal cycle (warming is greatest in the cold seasons) and vertical structure (warming is most pronounced near the ground). But — the amplitudes observed today are most like the GCM forecasts for around 2020. Not something to send you off to bed with sweet dreams, exactly.

Mark also pointed to some impacts of sea ice loss:

  • There has been a decline in prime polar bear habitat in many places, but also some increase in polar bear habitat in the central Arctic. The latter will disappear eventually, as summer sea ice continues to retreat.
  • The Northwest Passage has opened. The Arctic will be increasingly opened to economic activity like oil drilling, with all the attendant environmental hazards and chances for political dispute
  • As noted in yesterday’s dispatch, Greenland melt has accelerated. This is connected with the reduction in sea ice, and in fact the 2007 Greenland melt spiked upward in concert with the anomalously low Arctic ice cover. To put the contribution of Greenland melt in perspective, IPCC 2006 put sea level rise at 1.28 mm/yr, but based on the latest GRACE data on ice sheet melt, the estimated number is now 2.2mm/yr, of which 30% is due to Greenland and 20% due to Antarctica. Every new revision seems to be upward, and it’s far from clear what the ceiling will be once things shake out.
  • There are major vegetation changes in the Arctic, visible in satellite chlorophyll data. Photosynthetic activity is increasing, and many areas are turning over from tundra to shrub vegetation, a process known as “shrubbification,” which is evidently some reference to Monty Python
  • Permafrost temperatures have increased. In Siberia, from 1956 to 1990 there has been a 20cm increase in the depth to which permafrost melts annually. Soil temperatures in the Arctic are going up. This is not just a response to warming air temperature; changes in snow cover matter as well.
  • Two interesting questions that emerged in the Q&A session concerned how polar bears survived the Eemian interglacial. It then came out that we don’t know whether the summer sea ice was gone or not during the Eemian. Another question, related to the “tipping point” issue is whether the loss of sea ice is a “bifurcation” where you go from the icy state to an ice-free state discontinuously when the temperature passes a threshold, or whether it’s a continuous transition. Mark feels that it’s probably a bifurcation, based on the effects of sea ice thinning, but it’s basically not really known yet.

    That’s all for tonight! Back tomorrow with more great stuff from AGU.

    Postscript: Alan Robock, president-elect of the Atmospheric Sciences Section, organized a very fine Chinese banquet for the Section. Entertainment was provided by the “Physics Chanteuse,” whose songs often could use a bit of tweaking for fidelity to basic physics, but were always entertaining. She did a lot of the Hy Zaret repertoire, though unfortunately didn’t seem to be up on Tom Lehrer. A snippet: The Sun is a mass/ of incandescent gas/ A gigantic Nuclear Furnace…

    45 Responses to “Live (almost) from AGU–Dispatch #2”

    1. 1
      Columbia says:

      My English not so good but thank for lovely site with information I looking for and need also.

    2. 2

      I read 1 abstract. It was great! You should mention that URL for abstracts again. I will read more of them as time permits. What will the URL for whole papers be?

    3. 3
      Michiel Schaeffer says:

      Thank you so much for your blog report!

      I remember having a great time during my visits to previous AGU fall meetings. Impressive organization & science.

      I moved from my home in The Netherlands to Rwanda. The science community here certainly needs our support and to hook back up with the global community. But I just as certainly miss an employer supporting me to attend the AGU…

      For us here “far away” in central Africa your AGU dispatches are like gems (causing less trouble than the ones found here, I might hope…)

    4. 4
      Juola (Joe) A. Haga says:

      Thank you for the lively despatch. Proximity to beer is serendipitous in English, Math, Philosophy, or Classics and, as you’ve demonstrated, is kindly to climatologosts. Glad you can keep your cool so well when learning of Mark Serreze’s thinking about 2020 turning into 2007. Does Katey Walter from U of Alaska Fairbanks turn up at AGU bull sessions? Not long ago on some site or other she appeared in a photo lighting up methane burbling up from permafrost. For all one knows she may be flaming out an earth-bound aurora to rival the Northern Lights, if she ain’t careful about temperature inversions. (Or have I got my atmospheric physics all wrong?– as I usually do when the ebullience of company, like Siberian methane, tips my balance into arm-waving.) Again, for your reporting, thank you. And apologies for my fan-fare.

    5. 5
      Stuart Jensen says:


      Much thanks. For the first word on what is most important to me, it’s fortunate that the beer was near.

      It’s also heartening to read your evaluation of the state of Geophysist. :)

    6. 6
      Brad Arnold says:

      My contribution is the additional unexpected warming vector of melting oceanic methane hydrate.

      There is a big big carbon reservior under the sea-an estimated ten thousand billion tons of methane trapped in ice on the ocean bottom. Most of this is in very deep water that will be very resistent to global warming’s heat pulse, but some is in vulnerable shallow water deposits.

      A sudden release into the air of less than 30 billion tons of methane (CH4) would be like doubling the CO2 level.

      Generally, as the Earth warms, carbon sinks will become carbon emitters. To avoid either abrupt climate change or runaway global warming, we would have to cut our emissions even further to compensate for increased natural emissions.

      55 million years ago volcanic activity triggered a chain reaction of runaway global warming, but we are emitting carbon gas over 30 times faster.

      The stronger the trigger, the sooner the runaway global warming chain reaction happens, the faster the runaway global warming chain reaction unfolds, and the much much more severe the warming episode.

      “We now have evidence from the Earth’s history that a similar event happened fifty-five million years ago when a geological accident released into the air more than a terraton of gaseous carbon compounds. As a consequence the temperature in the arctic and temperate regions rose eight degree Celsius and in tropical regions about five degrees, and it took over one hundred thousand years before normality was restored. We have already put more than half this quantity of carbon gas into the air and now the Earth is weakened by the loss of land we took to feed and house ourselves. In addition, the sun is now warmer, and as a consequence the Earth is now returning to the hot state it was in before, millions of years ago, and as it warms, most living things will die.” (The Revenge of Gaia)

    7. 7

      Great post.

      I think Serreze is one of the most articulate scientists in the world working on Arctic ice.
      Anyone who wants to see a video of him speaking (plus his PPT slides) can go here).

    8. 8
      O.T. says:

      Sorry to go off on a tangent, but I was wondering if you could comment on the Bali conference, especially re the following report

      [Response: These guys are just jokers, and Monckton in particular seems to live in an alternate reality. They are justifiably being ignored in Bali (and elsewhere). – gavin]

    9. 9
      Ray Ladbury says:

      Re #8. I wonder if either Monckton or Inhofe would recognize reality if it passed them on the street. One suspects that Monckton is just relishing the fact that he has found the key to his 15 minutes of fame. He doesn’t care whether what he says is true or not. Inhofe really actually seems to be a true believer–now that’s sad!

    10. 10
      SecularAnimist says:

      FYI, an Associated Press article on CNN’s website quotes Mark Serreze (and in fact uses his quote as the title of the article):

      An already relentless melting of the Arctic greatly accelerated this summer, a warning sign that some scientists worry could mean global warming has passed an ominous tipping point. One even speculated that summer sea ice would be gone in five years.

      Greenland’s ice sheet melted nearly 19 billion tons more than the previous high mark, and the volume of Arctic sea ice at summer’s end was half what it was just four years earlier, according to new NASA satellite data obtained by The Associated Press.

      “The Arctic is screaming,” said Mark Serreze, senior scientist at the government’s snow and ice data center in Boulder, Colorado.

      Just last year, two top scientists surprised their colleagues by projecting that the Arctic sea ice was melting so rapidly that it could disappear entirely by the summer of 2040.

      This week, after reviewing his own new data, NASA climate scientist Jay Zwally said: “At this rate, the Arctic Ocean could be nearly ice-free at the end of summer by 2012, much faster than previous predictions.”

      So scientists in recent days have been asking themselves these questions: Was the record melt seen all over the Arctic in 2007 a blip amid relentless and steady warming? Or has everything sped up to a new climate cycle that goes beyond the worst case scenarios presented by computer models?

      “The Arctic is often cited as the canary in the coal mine for climate warming,” said Zwally, who as a teenager hauled coal. “Now as a sign of climate warming, the canary has died. It is time to start getting out of the coal mines.”

    11. 11
      Andrew Sipocz says:

      Could you clarify the current GRACE sea level rise estimate you give? Does the 2.2mm/year include global sea level rise including thermal expansion or is it simply the contribution from melting ice (i.e. the actual increase in mass)? I think this is confusing a lot of folks, me included. The satellite estimates from 1992 to present from Colorado indicate 3.3mm/year.

      And remember, when asked if you’re ready for another; “A beer is never more than 30 seconds from being finished”.

      [Response: The 2.8mm/yr I quoted includes everything — the thermal expansion as well as ice sheet melt. The increase relative to IPCC is largely due to Greenland ice sheet dynamics. By the way, the number Lonnie Thompson quoted Wednesday is 3.2 mm/yr rather than 2.8. There are various ways to estimate the ice sheet loss, which may account for the difference. –raypierre]

    12. 12
      Dr. J says:

      I agree on your comment about the young talent. I have been coming to Frisco AGU for many years and this year is showcasing much new talent (the poster sessions are superior), even if much of it is not American citizens. Like last year there is much discussion among those with “geophysics” in our resume education and working experiences curious of those here that don’t have those credentials. The number of non-geophysicists has been growing over the last few decades that come to Frisco, parallel to the climate hype of course, and the desire of AGU to expand far outside it’s original charter for more money and policy clout. The atmospheric group at AGU has grown like topsy over the last few decades, fueled by research dollars pouring into the field. There has also been much discussion of the activism and “framing” of incomplete and one-sided science for political purposes, like last year. Many are still uncomfortable with it, me included.

    13. 13
      Fred Mann says:

      I don’t know if this is the best place to ask, but …
      Roughly, how much of the predicted future warming, according to the IPCCs official stance, will be attributable to human activity?

      [Response: All of it. It may be reduced slightly or enhanced by changes in solar or volcanic activity in the future, but those changes are unpredictable. Therefore, IPCC just deals with the net effect of human activity. – gavin]

    14. 14
      ICE says:


      thank you so much for this great reporting – hope you can keep up the pace !

      one question:
      “The state of ice thickness observed in 2007 is quite similar to the modelled state in 2020.”
      i thought we didn’t have reliable global measurements of sea ice thickness yet?
      does this refer to satellite measurements ?

      [Response: We don’t have long term records on ice thickness, except from nuclear subs, but Mark referred to data from IceSat in connection with the above figures. I don’t know how the instrument works. It was news to me that such a thing existed. That’s what we go to AGU for! (that and the sushi). –raypierre]

    15. 15
      Chris O'Dell says:

      Thanks so much for the AGU blogging Raypierre! I couldn’t go this year, so it’s great to get to keep up with some of the climate stuff from afar!

    16. 16
      Janne Sinkkonen says:

      Related to the ongoing disappearance of arctic sea ice: How would the climate of northern continental regions, such as Finland, be affected if the summer ice disappeared right now? Or, does the unexpectedly fast melting result in unexpected changes in the climate of nearby regions?

      [Response: I have been wondering about this myself. I like to go spring skiing in äkaslompolo whenever I can, and I notice I’ve been using klister (liisteri) more and more, where as 15 years ago it was always blue wax in mid-April. There is a lot of good local work on this but not yet related to the sea ice melt. I’ve started trying to formulate a plan to sort that out by model simulations. Meanwhile, I’m reading papers. I was also prompted to think about this by seeing the exhibit in the climate room at Siida in Inari last summer, which seemed singularly weak on the matter of what Sapmi would be like in 2100. –raypierre]

    17. 17
      Lynn Vincentnathan says:

      RE “a few more years of the AGW signal rising above the background variability. This is true not just for global means, but for regional climate.”

      Are there still some places in the world that are getting colder? Or are all places now either warming or staying the same?

      I know in STATE OF FEAR Crichton made much of a few places that were getting colder (seems he didn’t learn about “average” or “mean” in school, as in “rise in the global mean temperature”), and I thought that sooner or later all places would be warming (or at least none would be getting colder) if the global warming trend continues (barring the halting of the thermo-haline conveyor, making the N. Atlantic colder).

      [Response: If you take a small enough “region” you can still find some places that are getting colder. Perhaps the interior Antarctic surface is the largest of these. Apart from that, for anything roughly as big as Europe, basically everything is warming now. –raypierre]

    18. 18
      Hank Roberts says:

      ICE, why do you think that? You can look it up.

      For example, the US Navy has published quite a bit of its older data on Arctic sea ice thickness, declassified thanks to then Senator Al Gore. The area declassified was referred to as the “Gore Box” on the Arctic ice maps. The Navy has also made scientific trips using their nuclear submarines.

      Ask for more help if you can’t find the information, let us know what searches you try and how far you get.

    19. 19
      SecularAnimist says:

      Off-topic, I guess, but a blog comment by a climate change denier points to this report — any comments from those knowledgeable enough to comment knowledgeably would be appreciated:

      New Study Increases Concerns About Climate Model Reliability
      December 12, 2007

      A new study comparing the composite output of 22 leading global climate models with actual climate data finds that the models do an unsatisfactory job of mimicking climate change in key portions of the atmosphere.

      This research, published online in the Royal Meteorological Society’s International Journal of Climatology, raises new concerns about the reliability of models used to forecast global warming.


      Scientists from [the University of] Rochester, the University of Alabama in Huntsville (UAH) and the University of Virginia compared the climate change “forecasts” from the 22 most widely-cited global circulation models with tropical temperature data collected by surface, satellite and balloon sensors. The models predicted that the lower atmosphere should warm significantly more than it actually did.

    20. 20

      raypierre, you’re blogging deserves a Kofax. There is none better.

      The reports you have given are shocking, even to those of us who follow climate change closely. Your reports are showing that not only has the Arctic sea ice just passed a tipping point, but the Arctic ocean and atmospheric circulation is beginning an irreversible change.

      The thin layer of fresh water over the Pacific and Atlantic water in the Arctic appears to be getting advected out of the Arctic. Oceanic heat release to the Arctic appears to be increasing rapidly. This could be the beginning of a change of global oceanic circulation patterns. Any comments on this hypothesis?

    21. 21
      Robert Edele says:

      Re #15: The effect on any locality can be highly variable and this rapid loss of sea ice was not forecast, so I would not put too much weight on local forcasts from the models.

      However, the high latitudes as a whole will get much warmer and wetter as a whole as a result of less ice cover. More open ocean means more evaporation and heat transfer, which means more rain and warmth for the locations that the moisture travels to. It’ll go somewhere, the unknown is where.

    22. 22
      Steve Bloom says:

      Ray, properly put I think that technical term should be “shrubberyfication.” It’ll be time to get really worried when we start seeing little white picket fences appear around those patches of shrubbery. :)

    23. 23
      John L. McCormick says:

      Ray, thank you for the on-the-scene reporting and the excellent commentary.

      According to your piece, Mark Serreze commented that:

      [Factors contributing to the unusual 2007 drop include an unusual pattern of atmospheric circulation, with high pressure over the Central Arctic and low pressure over Siberia. This brings a lot of warm air into the Arctic. How does this fit into the longer term pattern? It comes back to the thinning again: the sea ice was so vulnerable to this situation (which has happened before) because it is so thin.]


      What came first, the high and low pressure which amplified the meltback; or, the rapid meltback (inflow of warm Pacific) which made the high and low formation possible and thus, amplified the meltback?

    24. 24
      Nigel Williams says:

      Brad 6. 30 billion of 10 thousand billion tonnes. 3e10 of 1e13 -> 3 of 1e3 Now that’s only zero point three percent of the ‘known’ calthrate reserves. Do we have sensor arrays sitting over the most vulnerable deposits giving us daily temperature by depth?

      With increased wind energy already turning over the southern ocean to the extent that it has diminished its ability to absorb CO2, that same overturning is, I imagine, moving energy deeper into the ocean. Recent events in the north Pacific and Arctic oceans imply similar processes leading to warming of the deeper waters. And no place is safe from this effect as ocean circulation will carry that energy away from the areas of stronger winds to other interesting places – some probably with calthrates ready to pop.

      Is there a map of calthrate disposits figured by relative vulnerability? (temperature, depth, strength of benthal currents, location wrt up-stream heat sinks etc)

      Is it fair to say that when this gas starts heading for the surface it will induce a convection motion in cells in the water column whereby the core of uprising water will be matched by an outer down current that will bring still more warm surface water down over the deposit which will hasten the rate of release and increase the area of release as well. So once the first bit of the calthrate deposit starts to gas, then the resulting convection system will see a rapid spread of bottom-temperature rise with consequent further release in a chain-reaction format.

      This process will only come to a halt when the calthrate in an area is depleted or the lateral leap to the next deposit is outside the influence of the convection cells.

      There are stories about ships disappearing in such gas bubbles. We could be looking at civilisations disappearing! Gulp.

      Has this convection process been modelled at any scale?

    25. 25

      Thank you for keeping us up to date on the presentations. The latest studies on the Arctic are particularly interesting. The situation is more critical there than originally predicted. If 2007 is the new 2020, then what will 2020 be? It’s not pleasant to contemplate.
      It’s especially gratifying to hear that capable young people are entering the field. It sounds like the future of climate science will be in good hands.

    26. 26
      Eli Rabett says:

      I’m curious about the SO2 photolysis issue

      [Response: It has to do with the question of how much SO2 you could build up on Early Mars. An idea that some colleagues at Harvard got me interested in. I have a handle on the infrared effects of SO2, but Kevin Zahnle thinks SO2 photolysis would wipe out the effect I’m hoping for. We shall see. –raypierre]

    27. 27
    28. 28
      Patrick 027 says:

      I’d love to hear more about “Studying Climate Dynamics with Idealized Atmospheric GCM’s”. (one thought – changing the longwave radiative properties of the atmosphere should affect the thermal damping of various kinds of waves like gravity waves and planetary waves, affecting perhaps the QBO and the occurence of sudden stratospheric warmings, and also the way energy from extratropical cyclones is exchanged between the troposphere and stratosphere (also affected by changing tropopause height and wind shear, I’d think). Anyboby working on that?)

      (Also, I would be very interested in what somebody from RealClimate thinks of “With Speed and Violence”. Half way through the book now myself. So far it looks mostly accurate (and indeed alarming) as far as I know, though I suspect some clarifications and corrections could be made (in rate of global warming at end of Younger Dryas (?), attribution of x% of last century’s warming to solar effects, changes in ‘deep time’ (author mentions neoproterozoic snowball earth but skips over any paleozoic glaciations – an understandable oversimplication given the primary subject matter, but still…), etc… At the same time I’ve learned that pollution tends to persist longer in the Arctic due to low atmospheric hydroxyl levels (due to less sunlight – UV in particular).)

    29. 29


      Sorry man. You missed this one.

      Shrubbification is of course in reference to our country’s leader President Bush. Molly Ivins (may the Great Spirit bless her soul) used to call him shrub when he was here in Texas. It would only be fitting for a significant feedback mechanism, a complicated little piece of climatology, to be named in reference, maybe not to the greatest climate change obfuscator of all times, but certainly to the most important.

      Thanks for all the important work that you guys do. And, yes we have crossed a threshold. I had to go see for myself this summer. Kangerlussuaq, Ilulissat and 2,000 miles in Alaska, and yes, things seem to have accelerated significantly.

      Bruce Melton
      Austin, Texas

    30. 30

      Regarding Polar Bears during the he Eemian interglacial – I read that the modern Polar Bear evolved from the Grizzly Bears over the past 100,000 years, so they didn’t even exist during the Eemian interglacial period (which was, I think, a bit over 100,000 years ago.) So it if the Arctic Ocean was ice free, maybe some other large mammal went extinct and the polar bear moved into its niche.

    31. 31
      Hank Roberts says:

      David, where did you read that, and how long ago?
      The facts may have changed; one jawbone was in the news as of a few days ago suggesting a longer time span:

    32. 32
      Bruce Tabor says:

      Re 29 David Kroodsma,

      Yes, I recently read in Six Degrees by Mark Lynas that polar bears have only recently separated from brown bears as a distinct species. Lynas has been reasonably careful to source his material from scientific literature.

      From Wiki:
      “…recent genetic studies have shown that some clades of Brown Bear are more closely related to polar bears than to other brown bears, meaning that the polar bear is not a true species according to some species concepts. In addition, polar bears can breed with brown bears to produce fertile grizzly–polar bear hybrids, indicating that they have only recently diverged and are not yet truly distinct species. But neither species can survive long in the other’s niche, and with distinctly different morphology, metabolism, social and feeding behaviors, and other phenotypic characters, the two bears are generally classified as separate species.”

      Page 8 of the following document gives two estimates of the divergence of brown and polar bears based on two papers:
      “Age models based on molecular studies of evolutionary relationships among extant species of bears differ considerably as to the divergence time of polar bears from grizzly bears. Wayne et al. (1991) suggested this happened 70,000 – 100,000 yrs ago while Yu et al. (2004) concluded this might have happened 100,000 – 150,000 yrs ago.”

    33. 33
      CobblyWorlds says:

      # 13 ICE,

      With regards ice thickness.

      Peter Wadhams is one of the people who’s been looking into this. There’s an essay of his here which alludes to the techniques used (direct measurement by submarine)
      I quote:
      “It is very difficult to measure ice thickness from satellites. Sea ice sheets contain
      cells of liquid brine which prevent satellite-based radar from penetrating to the bottom.
      Methods that depend on measuring the height of the top surface above sea level (radar
      and laser altimeters) suffer from our lack of knowledge of snow depths and of snow and
      ice density. The best solution has proved to be measurements from below by moving
      vehicles, that is, submarines. Since 1958 the US has been sending submarines under the
      Arctic ice and profiling the draft of the ice using upward looking sonar. They were
      joined in 1971 by UK submarines, and since that time every UK submarine voyage to the
      Arctic has included a scientist in its complement, usually myself…”
      “The most startling result of the work of our US colleagues and ourselves was our
      independent discoveries that the Arctic ice has been undergoing a dramatic thinning.
      Comparison of data from the 1970s and from the 1990s shows a mean loss of more than
      40% of thickness during this period. The US and the UK data covered different regions of
      the Arctic but gave the same percentage loss of thickness.”

      I’ve got some more stuff of his e.g.
      “Measurement of Arctic sea-ice thickness by submarine 5 years after SCICEX” Hughes/Wadhams Annals of Glaciology 44 2006. and conference proceedings from World Climate Research Programme Tromso Norway April 2002. I think I got these from Nick Hughes’ pages at – but that site’s down right now.

      Hope this helps.

    34. 34
      CobblyWorlds says:

      From the BBC: With regards a presentation at the AGU.

      “Scientists in the US have presented one of the most dramatic forecasts yet for the disappearance of Arctic sea ice.

      Their latest modelling studies indicate northern polar waters could be ice-free in summers within just 5-6 years.

      Professor Wieslaw Maslowski told an American Geophysical Union meeting that previous projections had underestimated the processes now driving ice loss.

      Summer melting this year reduced the ice cover to 4.13 million sq km, the smallest ever extent in modern times.

      Remarkably, this stunning low point was not even incorporated into the model runs of Professor Maslowski and his team, which used data sets from 1979 to 2004 to constrain their future projections.”

      If I am not mistaken: I still see good reason to view perennial ice as a damping factor on the summer’s powerful ice-albedo feedback. From that broad brush point of view bifurcation seems likely once the ice is thinned to a certain point. However as Mark Serreze is quoted in that article:
      “I think Wieslaw is probably a little aggressive in his projections, simply because the luck of the draw means natural variability can kick in to give you a few years in which the ice loss is a little less than you’ve had in previous years. But Wieslaw is a smart guy and it would not surprise me if his projections came out.”

    35. 35
      Nick Gotts says:

      Re #30 I wonder how certain it is that the jawbone found is from a member of Ursus maritimus – the polar bear we know now. Ursus maritimus is very closely related to Ursus arctos, the brown (including grizzly) bear: the two produce fertile offspring and sometimes interbreed in the wild, as confirmed by DNA testing of a bear shot in Canada in 2006 (which incidentally raises the question of whether they should be regarded as separate species). Mammalian adaptation to Arctic conditions is in many ways predictable (e.g. white fur, shorter limbs, and most relevant in this case, smaller facial features), so it may be that the “polar bear” as a phenotype became extinct in the Eemian, then re-evolved. The re-evolved version would not be exactly the same, but with a single jawbone to go on, I doubt this possibility can be ruled out.

    36. 36
      Nick Gotts says:

      Re #31. p.s. You’ll probably find more than you ever knew you wanted to know about hybrid bears at

    37. 37
      Urs Neu says:

      Concerning the effects of rapid Arctic sea ice melting

      If Arctic sea ice is retreating much faster than projected, this might also have effects far beyond the Arctic region. Stronger Arctic sea ice retreat means a faster amplification of Arctic warming which leads to a more rapid decrease of the Pole-Equator temperature gradient. And this could have implications on other related changes (northward shift of storm tracks, northward extension of the Hadley cell), at least in summer and autumn. Thus, some of the expected related changes (e.g. more and longer droughts in subtropical regions like the Mediterranean or even more northwards) could maybe also happen much faster than expected. What do you think?

    38. 38
      inel says:

      Re #13 and #31. Looks like Peter Wadhams of Cambridge University presented at AGU Cryosphere Group in SF on Tuesday. The abstract was listed as:

      Arctic Sea Ice Thickness – Past, Present And Future
      Wadhams, P
      Dept. of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA, United Kingdom
      In November 2005 the International Workshop on Arctic Sea Ice Thickness: Past, Present and Future was held at Rungstedgaard Conference Center, near Copenhagen, Denmark. The proceedings of the Workshop were subsequently published as a book by the European Commission. In this review we summarise the conclusions of the Workshop on the techniques which show the greatest promise for thickness monitoring on different spatial and temporal scales, and for different purposes. Sonic methods, EM techniques, buoys and satellite methods will be considered. Some copies of the book will be available at the lecture, and others can be ordered from the European Commission. The paper goes on to consider early results from some of the latest measurements on Arctic sea ice thickness done in 2007. These comprise a trans-Arctic voyage by a UK submarine, HMS “Tireless”, equipped with a Kongsberg 3002 multibeam sonar which generates a 3-D digital terrain map of the ice underside; and experiments at the APLIS ice station in the Beaufort Sea carried out by the Gavia AUV equipped with a GeoSwath interferometric sonar. In both cases 3-D mapping of sea ice constitutes a new step forward in sea ice data collection, but in the case of the submarine the purpose is to map change in ice thickness (comparing results with a 2004 “Tireless” cruise and with US and UK data prior to 2000), while for the small AUV the purpose is intensive local mapping of a few ridges to improve our knowledge of their structure, as part of a multisensor programme.

      Perhaps someone has a copy of his most up-to-date paper? In any case, the book he refers to, as co-editor, is available here:

      In that book, there is a section titled ‘Arctic Sea Ice Thickness – A Review of Current Techniques and Future Possibilities’ by Peter Wadhams that is most interesting. You can find it on pages 12 through 21.

      You might also like to look up NASA’s ICESat mission, which uses a laser altimeter (GLAS).

      The ESA will be launching CryoSat-2 in 2009, which uses a radar altimeter/interferometer (SIRAL) and the mission is supported by intrepid explorers taking measurements of snow thickness on foot!

    39. 39

      Re #30
      I read it in Mark Lynas’ book, Six Degrees. He has lots of citations, but no citation for that claim, now that I look. It would be interesting to know who is right! I’m not much of an evolutionary biologist, so I have no idea how much speciation takes place in 100,000 years, but I would think geneticists would be able to figure out how long ago brown bears and polar bears were the same species.

    40. 40
      Chuck Booth says:

      Re #33, #37 David Kroodsma and Nick Gotts on polar bears

      This site may have the information you are looking wondering about:

      “Talbot and Shields (1996b) found mtDNA sequence divergence rates similar to those reported by Cronin et al. (1991), and proposed that ancestors of the Alexander Archipelago brown bears diverged from the other mtDNA lineages of brown bears 550,000� to 700,000 years ago. The mtDNA sequence divergences also suggested that polar bears branched from the Alexander Archepelago ancestral stock of brown bears about 200,000 �to 250,000 years ago, a date closely corresponding with that suggested in the fossil record (Thenius 1953; Kurt�en 1964)….”

    41. 41
      Bruce Tabor says:

      Re. 29, 30, 37 Polar Bears.
      This is somewhat frustrating as I posted a reply about polar bears 18 hours ago and its not appeared.

      Basically the following document contains two published estimates of the date of divergence of polar and brown bears:
      “Age models based on molecular studies of evolutionary relationships among extant species of bears differ considerably as to the divergence time of polar bears from grizzly bears. Wayne et al. (1991) suggested this happened 70,000 – 100,000 yrs ago while Yu et al. (2004) concluded this might have happened 100,000 – 150,000 yrs ago.”

      The refernces are:
      Wayne, R.K., B.V. Valkenburgh, and S.J. O’Brien. 1991. Molecular distance and divergence time in carnivores and primates. Molecular Biology and Evolution 8(3):297-319.
      Yu, L., Q-W. Li, O.S.Ryder, and Y-P. Zhang Y-P. 2004. Phylogenetic relationships within mammalian order Carnivora indicated by sequences of two nuclear DNA genes. Molecular Phylogenetics and Evolution. 33: 694-705.

      Re. 30. Can a jaw bone could be used to distinguish polar and grizzly bears? Even so the date is 110-130 kyr – the warmiest peak of the Eemian was around 125kyr – and speciation would first involve isolation of a sub-population of grizzly bears and then divergence. A jaw bone would not reveal whether polar bears had yet become dependent on sea ice for habitat.

      Note that polar bears can interbreed with grizzlies and produce fertile offspring:
      “However, more recent genetic studies have shown that some clades of Brown Bear are more closely related to polar bears than to other brown bears, meaning that the polar bear is not a true species according to some species concepts.In addition, polar bears can breed with brown bears to produce fertile grizzly–polar bear hybrids, indicating that they have only recently diverged and are not yet truly distinct species.”
      The Wiki site has the date of divergence at roughly 200,000 years ago.

    42. 42
      Boslough says:

      Three questions:

      1) During his Arctic amplification discussion, Mark Serreze showed a 2D plot of Arctic temperature anomaly with month on the horizontal axis and year on the vertical. It clearly showed the winter temperatures increasing much more rapidly than summertime temperature. I can’t remember what he called this plot but I wonder if it can be posted here.

      2) I missed Lonnie Thompson’s talk. Was it a one-time broadcast stream or is it archived somewhere?

      3) There was a great question after the Serreze presentation regarding geophysical risk terminology. A seismologist (I think) pointed out that bridges and buildings in California must be constructed to take into account the most *conservative* estimate of potential seismic loading, meaning the worst case (maximum possible displacement over maximum possible length). But the *conservative* estimate of climate risk would be the most optimistic case (minumum possible change). She asked if it wasn’t time for climate scientists to use the word *conservative* the same way everybody else does when referring to risk.

    43. 43
      CobblyWorlds says:

      #35 Urs Neu,
      I think that the climate implications of a rapid transition to a seasonally ice-free Arctic Ocean MIGHT be the primary current issue for policy makers.

      IF we can expect a detrimental impact on precipitation distribution and/or timing within a couple of decades at the outside, then in terms of infrastructure/argicultural timescales, NOW is the time to act (if Mazlowski’s correct it may be too late to anticipate – our only attainable option would be reaction).

      However I am unable to get a handle on the problem, and I’m not sure this is due to my lack of a formal education in this matter. I get the impression nobody knows.

      I’ve recently read Seidel et al which, to me, hammers home the point that we don’t seem to know enough to convert a broad grasp of largescale atmospheric process response into specific guidance on impacts. They discuss the widening of the tropics. Which may not seem immediately relevant to some reading this, but the tropics are in the most basic sense just the hot end of the atmospheric heat engine, the poles being the cold end.

      Your suggestion of drought interests me because it’s the sort of pattern outlined in Seager et al. However that’s with respect to a projected pattern of GW, which does not seem to me to be the same as an ahead-of-schedule seasonally ice-free Arctic. One major issue is that a rapid loss of Arctic ice would cause a rapid reduction in pole-equator heat gradient. Ultimately GW would do likewise but it seems to me that this could bring elements of that issue ahead of time – large scale climatic system changes without the associated projected degree of warming. Furthermore the implications of increased latent heat from evaporation seem to me to make this a special case.

      To quote from Serreze et al:
      “In their modeling study,Magnusdottir et al. (36)
      found that declining ice in the Atlantic sector promotes
      a negative NAO-NAM atmospheric circulation
      response, with a weaker, southward-shifted
      storm track. Singarayer et al. (37) forced the Hadley
      Centre Atmospheric Model with observed sea ice
      from 1980 to 2000 and projected sea-ice reductions
      until 2100. In one simulation, mid-latitude storm
      tracks were intensified, increasing precipitation over
      western and southern Europe in winter. Experiments
      by Sewall and Sloan (38) revealed impacts on
      extrapolar precipitation patterns leading to reduced
      rainfall in the American West. Although results
      from different experiments with different designs
      vary, the common thread is that sea ice matters.”

      Is there reason to start ringing the alarm bells on this?

      Are our governments being appraised of the risk that the situation in the Arctic could mean much much more than just the risk of Polar Bears allegedly drowning?

      Will news like this get worse more quickly than most of us fear?
      BBC News:
      “World wheat prices have risen to a 10-year high following a dramatic fall in harvests sparked by a severe drought in Australia and crop diseases across parts of Europe and the Americas. Meanwhile, demand for wheat-based produce is reaching record levels and the land once used to grow wheat is being threatened by the demand for biofuel crops.”

      Seidel et al
      “Widening Of The Tropical Belt In A Changing Climate” Science May 2007

      Seager et al
      “Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America.” Nature 2007.
      final pre-print pdf –

      Serreze et al
      “Perspectives on the Arctic’s Shrinking Sea-Ice” Science 16/3/07
      (sorry can’t find a free pdf)

      #36 Inel,
      Thanks for all that. The book you link to is very comprehensive. ICE should find all they need there.

      #39 Bruce Tabor, lost post? – same here. I keep a scratchpad to keep copies of posts on boards in case of this.

    44. 44
      Ray Ladbury says:

      Boslough asked: “3) There was a great question after the Serreze presentation regarding geophysical risk terminology. A seismologist (I think) pointed out that bridges and buildings in California must be constructed to take into account the most *conservative* estimate of potential seismic loading, meaning the worst case (maximum possible displacement over maximum possible length). But the *conservative* estimate of climate risk would be the most optimistic case (minumum possible change). She asked if it wasn’t time for climate scientists to use the word *conservative* the same way everybody else does when referring to risk.”

      Ooh! Excellent question! This question provides an excellent illustration of the difference between science and engineering. A scientist is interested in whether an effect is present and in how significant it could be for the physical system. A scientist is interested in HOW the system works. An engineer is interested in WHETHER it will work–or more specifically, whether it will fulfill its intended function.
      This is probably one reason why the economic analyses (with the exception of the Stern Report) have tended to be rather complacent. Economics has to worry about how the system fulfills its purpose. As such, it should be done using engineering estimates, rather than scientific analyses.

    45. 45
      Hank Roberts says:

      “Cause of El Nino” is gemcontent is a linkspammer, probably a bot — suggest breaking the link or deleting the post

    Switch to our mobile site